Add support for defining `Job` controller

[surajssd]

Right now we by default create Deployment as the controller, so come up with a way to define the Job controller.

Read more about job:

• Writing Job: https://kubernetes.io/docs/concepts/workloads/controllers/jobs-run-to-completion/
• Job API docs: https://kubernetes.io/docs/api-reference/v1.6/#job-v1-batch
• Also look at cron job: https://kubernetes.io/docs/concepts/workloads/controllers/cron-jobs/

[kadel]

Cron jobs are still alpha feature. I don't think we should add support for it until they are out of alpha.

But Jobs are in stable v1, and we should definetly support that.

[concaf]

Talking with @kadel, we thought that -

• JobSpec is a lot similar to DeploymentSpec, in the sense that there are top level fields and then there is PodTemplateSpec, so maybe we can treat this similar to how we reuse the PodSpec.

So, we can do something like this with jobs -

type JobSpecMod struct {
    Name                string
    api_v1.PodSpec      `json:",inline"`
    ext_v1beta1.JobSpec `json:",inline"`
}

type App struct {
    Name              string             `json:"name"`
        ...
        ...
    Jobs              []JobSpecMod       `json:"jobs,omitempty"`
}

This lets us defining jobs like -

name: httpd
containers:
- image: centos/httpd
services:
  - name: httpd
    type: NodePort
    ports:
    - port: 8080
      targetPort: 80
jobs:
- name: piStuff
  activeDeadlineSeconds: 100 # part of JobSpec
  containers: # part of PodSpec
  - name: pi
    image: perl
    command: ["perl",  "-Mbignum=bpi", "-wle", "print bpi(2000)"]
  restartPolicy: Never

This also means, that defining solo jobs will be possible like -

name: httpd
jobs:
- name: piStuff
  activeDeadlineSeconds: 100 # part of JobSpec
  containers: # part of PodSpec
  - name: pi
    image: perl
    command: ["perl",  "-Mbignum=bpi", "-wle", "print bpi(2000)"]
  restartPolicy: Never

How does this look @kedgeproject/maintainers? Lazy consensus in effect! :yum:

[concaf]

@kadel also, about the name auto generation part, I think it's safe to auto generate names for any number of jobs specified in the spec, since there are no services, etc associated with these, and no one talks to them (which is sad) but they need to communicate outside.

[surajssd]

Since https://github.com/kedgeproject/kedge/pull/253 is merged closing this one!